A dispersant for cement is widely used as a water-reducing agent for cement compositions such as cement paste, mortar and concrete, and has become essential in constructing civil engineering and building structures and the like from cement compositions. Such dispersant for cement increases the fluidity of cement compositions and thereby reduces the water requirement of the cement compositions, and is therefore effective in improving the strength, durability and the like of hardened products. Among such dispersants for cement, those comprising a polycarboxylic acid copolymer exhibit superior water-reducing performance to naphthalene- and other polycondensate-based water reducing agents.
For example, the following polycarboxylate dispersants for cement are disclosed: an additive for cement, mortar and concrete, which is composed of polycarboxylic acid superplasticizers resulted from partial crosslinking polymerization of monomers (CN101817657A); a cement admixture including a copolymer obtained by polymerization of a polyalkylene glycol diester monomer having an unsaturated bond and an acrylic acid-based monomer, and/or a metal salt of the copolymer (JP-A Hei 05-238796); a cement admixture including a water-soluble polymer produced by polymerization of a (poly)alkylene glycol monoalkenyl ether monomer and a polyfunctional unsaturated monomer (JP-B 3946998); a cement additive including a polycarboxylic acid copolymer containing at least an unsaturated polyalkylene glycol ether monomer and an unsaturated mono(di) carboxylic acid monomer as monomer components, and/or its salt, and a polyalkylene glycol derivative (JP-B 4394765); a fluidity retaining agent for freshly mixed cement paste, mortar, concrete and the like, in particular a multi-branched polycarboxylic water reducer with an excellent performance in slump retention (CN101851323A); a dispersant for a hydraulic composition which includes a copolymer containing an alkylene glycol ether monomeric unit, a maleic acid monomeric unit, and a half ester monomeric unit of a maleic acid monomer unit and an alkylene glycol compound (JP-B 4015088); or the like.